In a microscope used for fluorescence microscopy, the focusing optics do not need to be moved a large distance in order to achieve the necessary degree of focus. Instead, only a small amount of movement is needed, but it is desirable that this movement be carried with a very high degree of accuracy, for example in small increments on the order of about 10 microns. Although existing microscopes have provided an adequate degree of accuracy in focus, this accuracy has not been entirely satisfactory. This is due in part to the fact that existing focus drives tend to have a degree of backlash that reduces the accuracy of the focus.
A further consideration is that, in fluorescence microscopy, light emitting diode (LED) devices are used as light sources. Sometimes it is necessary to change a light source, for example to replace an LED that has failed, or to change the color (wavelength) of the illumination. In order to change a light source, it is typically necessary to carry out a significant degree of disassembly of the microscope in order to reach the light source. Moreover, where the replacement is being carried out in order to adjust the wavelength of the illumination, it may also be necessary to adjust the focal length, and/or change some optical components such as lenses and/or filters. This can involve replacing several independent components. As a result, the overall procedure, while adequate for its intended purposes, tends to be time consuming, and can involve replacement of multiple components on an item-by-item basis.